#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/wait.h>
#include<sys/types.h>
#include<unistd.h>


#define SEP " "
#define SIZE 64
#define NUM 1024

int lastcode = 0;
char cwd[1024];
char enval[1024];

const char* getUsername()
{
   const char *name =  getenv("USER");
   if(name) return name;
   else return "none";
}


const char* getHostname()
{
   const char *hostname =getenv("HOSTNAME");
   if(hostname) return hostname;
   else return "none";
}

const char* getCwd()
{
   const char *cwd = getenv("PWD");
   if(cwd) return cwd;
   else return "none";
}

int getUserCommand(char* command,int num )
{
    
    printf("[%s@%s %s]#",getUsername(),getHostname(),getCwd());
    char *r = fgets(command,num,stdin);
    if(r == NULL) return -1;
    command[strlen(command) - 1] = '\0';
   return strlen(command);
}

void commandSplit(char* in,char *out[])
{
    int argc = 0;
    out[argc++] = strtok(in,SEP);
    while(out[argc++] = strtok(NULL,SEP));
#ifdef Debug 
    for(int i = 0; out[i]; i++)
    {
        printf("%d:%s\n",i,out[i]);
    }
#endif
}

int execute(char* argv[])
{

    pid_t id = fork();
    if(id < 0) return -1;
    else if(id == 0)//child
    {
        execvp(argv[0],argv);
        exit(1);
    }
    else //father 
    {
        int status = 0;
        pid_t rid = waitpid(id,&status,0);
        if(rid > 0)
        {
            //获取退出码
            lastcode = WEXITSTATUS(status);
        }
    }
    return 0;
}

void cd(const char* path)
{
    chdir(path);
    char tmp[1024];
    getcwd(tmp,sizeof(tmp));
    sprintf(cwd,"PWD=%s",tmp);//bug，解决是将cwd设置为全局的
    putenv(cwd);
}

int doBuildin(char* argv[])
{
    if(strcmp(argv[0],"cd") == 0)
    {
        char* path = NULL;
        if(argv[1] == NULL) path = ".";
        else path = argv[1];
        cd(path);
        return 1;
    }
    else if(strcmp(argv[0],"export") == 0)
    {
        if(argv[1] == NULL) return 1;
        strcpy(enval,argv[1]);
        putenv(enval);
        return 1;
    }
    else if(strcmp(argv[0],"echo") == 0)
    {
        char* val = argv[1]+1;
        if(strcmp(val,"?") == 0)
        {
            printf("%d\n",lastcode);
            lastcode = 0;
        }
        else 
        {
            printf("%s\n",getenv(val));
        }
        return 1;
    }
    else if(0){}
    return 0;

}

int main()
{
    char usercommand[NUM];
    char* argv[SIZE];
    while(1)
    {

    //1.打印提示符&&获取用户的指令
    int n = getUserCommand(usercommand,sizeof(usercommand));
    if(n <= 0) return 1;
    //2.分割字符串
    //"ls -a -l" --- "ls" "-a" "-l"
    commandSplit(usercommand,argv);
    //3.check build -in command 
    n = doBuildin(argv);
    //4.执行对应的命令
    if(n) continue;
    execute(argv);
    }
    return 0;
}
